Then why are there new bug reports specific to TBP?
Because we have fans who develop missions and campaigns. Sometimes they report bugs with the game engine.
So then, while the mod has officially lost the support of its creators, it continues to live on through its fans. Its fans then, I would imagine, are more than welcome to modify, tweak, etc the mod to their hearts content. If a new team decides to carry on the torch, they should feel free to, perhaps under a modified name (a la Desert Combat vs Desert Combat Extended for BF1942). If anyone is interested I'm sure that shouldn't be a problem.
And if it's dead, why is there a problem with the SCP dropping support for it?
None. The SCP team can do as they please. We don't tell other teams what to do. One might expect some attempt at backward compatability such that the end user experience of TBP in 3.6.10 is comparable with 3.6.9 but that's all one can reasonably expect.
Then I find your "Open Warning" post a bit offensive, as you seem to be telling people what should already be common sense. When a developer stops supporting a piece of software, it's a bit far fetched to expect the developers of software that product relies on to continue to worry about supporting it, don't you think? You're basically warning people that if they stop working on their project, at some point down the line it might not work anymore and that the SCP team is somehow in the wrong when this happens. Otherwise, it sounds more like you have a problem with _how_ this decision process was being handled, including the posting in TBP's internal forum (which I don't initially see a problem with a HLP admin doing), and the subsequent antics. If that's so, I think your warning was still a bit misplaced.
Also, the SCP credo has always been 'retail compatibility first'. There was, to my knowledge, no similar promise for mods. I suppose it was always assumed that a mod could be patched to work properly with future versions. This might be one of the first times where such a case has arisen. I don't remember another one anyway.